Breaking Down

[John M.]

This is a 66 BB with only a few miles since resto.
It runs pretty good until you get into hard and when it gets up to about 3000 RPM it starts to break down. If you accelerate slowly it doesn't.
All stock points, coil, carb, etc. Dwell OK, initial timing advanced about 10 degrees.
Going to check points and float levels and change distributor cap and coil. Any other ideas, clues?
Thanks
John McRae 30025

[Timothy B.]

Re: Breaking Down

John,

I think you are on the right track looking at primary and secondary ignition. I would change things one at a time and start with the coil.

[William C.]

Re: Breaking Down

What are you using for plug wires?

[Michael G.]

Re: Breaking Down

John,

I think you are on the right track looking at primary and secondary ignition. I would change things one at a time and start with the coil.

I'm with you Tim.....one change at a time. Analyze, move forward. Myself would start with known coil....points next. I've observed a coil that would start the engine however would crap out in upper RPM range.

[Bill M.]

Re: Breaking Down

Check the fuel filter too.

[Ronald L.]

Re: Breaking Down

By breaking down you mean stumble? If so mine's doing a little of the same, out for a nice calm drive, nada, step into it and around 3000 it really breaks up, old carb, original coil, new wires, I suspect the carb I doubt it has ever been rebuilt.

[Timothy B.]

Re: Breaking Down

Ronald,

The general rule of thumb is to make sure ignition is up to snuff before carburetor work. Things like points, coil, dirty advance mechanism inside distributor are easy to address and not very expensive to repair.

I would start there first and then make sure the carburetor is getting a unrestricted flow of fuel.

[Joe M.]

Re: Breaking Down

If you used an old gas tank and the car sat it could be accumulated debris. Fuel filter might be the culprit as suggested. Fuel pump pressure vs carb requiements?

[John M.]

Re: Breaking Down

Thanks for the replies.
The first thing we did was change the coil, expecting the same thing but it took off like a shot at 2500 RPM with only the slightest hesitation, whereas before it would break downuntil you let off on the gas.
The coil wires are new Lectric Limited (we have had problems with these before)and the points are new Delco's. We quit after that run and will clean and check coil, cap and wires but I think we're there.
Thanks very much

[Larry M.]

Re: Breaking Down

John:

If the point set is DELCO #106P or PS, they will be limited to around 5000 - 5500 RPM max before point bounce. If you want more RPM then you need to get the DELCO #112P or buy the high performance set from Accel. I can provide the part number if needed.

The archives also contain the part numbers for other brand high performance points sold by NAPA and others. Just do a search.

Larry

[Duke W.]

Re: Breaking Down

The Delco D112P are long discontinued, but Standard Motor Products still makes an equivalent set. It's available under several brands/part numbers, like NAPA CS89.

Duke

[John M.]

Re: Breaking Down

Thanks guys,
this is a stock 390 horse car and our problem was down at 2-3000 under hard acceleration on an engine with a 53-5500 redline. It will never go over 5000-5500 with us but maybe the new owner will try??
Should we install those points anyway? It's a cheap enough fix.

[Duke W.]

Re: Breaking Down

The standard tension set is fine assuming that the distributor is in decent condition - no wobbly breaker plate or sloppy bushings.

I only recommend the high breaker arm tension set for engines with redlines over 5500.

You can test the basic condition of the distributor by free revving the engine up to 5000-5500 while watching the dwell angle.

If it drops more than about 2 degrees, there's likely a distributor problem.

If the points behave okay at high revs, then misfiring under load is probably somewhere on the high voltage side, which could include the coil.

Duke

[Larry M.]

Re: Breaking Down

The Delco D112P are long discontinued, but Standard Motor Products still makes an equivalent set. It's available under several brands/part numbers, like NAPA CS89.

Duke

I agree, but the 112P is still available in the secondary market if you search. Plus one set may last a lifetime, the way we now drive these cars.

I have 3-4 sets of 112P on my storage shelf that I bought a few years back, but as JoeL says "they are not for sale".

The NAPA CS89 you mentioned or the Accel brand are both excellent alternatives that are easy to get.

[Ronald L.]

Re: Breaking Down

In my case, back in the spring I reved the engine while checking dwell - it was stable as a rock. This past week I changed the fule filter - even though it was "not old" and it was clean inside as is the gas tank & lines and we are at less that 2% alcohol left over from the springs initial fill.

Will look into the points & the like again...